normally i load it one Pack level and fix them down,and then the Top Pack which i strap down too.
If you just strap Top-Pack down the lower one may slip in emergency Brake
Not sure how to help you with the strapping part, but on offloading I take it they are in bundles ? . get forkie to take off half of 1 x side on the front first, turn round then he takes half the other side off at the rear, repeat until finished, stops the bum squeaking,.
Turns out I was sent to a different place for delivery,
told forkie my plan of under slinging the straps and he says “cant drive not allowed to stand on the part loaded timber”
so i says “you will have to get me ladders” he huffed and puffed and went away and said there was a proper set of stairs you know the one’s with the wheels but these were proper rusty (i dont know why they were not offered the before maybe cos I did not ask 
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but by then I managed to throw the straps through the gap at top 
Only reason I says curtain sider, i shoud have mentioned I drive a wag & drag dont know if that would make any difference tbh, but have took on board all advice cheers just started learning, time to move on
Try getting a plank of wood or some long thing to push the strap across the top of the load.
If the timid ■■■■ won’t help marshall the traffic then ■■■■■ him & his load. Cheeky prick.
Try throwing the straps over before the forky loads it on to the trailer.
Say you are loading 3high on each side, load the 3 on one side throw the strap over, but loop the strap towards the end of the top pack so it does not get caught in the middle. When 3 are put on other side slide strap horizontally across, bingo both sides covered ratchet down. No need to climb on back at all.
Alternatively throw end of strap over roof, if trailer is not too high, clip on to side of trailer, so when looking from back the strap looks like a diagonal line from roof to floor. When timber is loaded it will automatically push the strap over both sides of packs, (only works if loaded on one side by reach truck. Hope you understand ,I aint the best at explaining things (as you have maybe already noticed 
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Next time I do the drop, i will just throw straps over timber and under roof, failing that will use said steps, also the tip about putting on straps where they dont come off as first packs come off the side then ratchet up is a really good one, i have to turn round anyway as its a little ind est with a dead end to the left, cars double parked on corner and the 5T weight restriction on to the right but with it being strapped down I may get away with turning in the yard entrance, would usually ask an old hand at the yard but am off today Cheers for all the advice